Features of the application of international quantum measurement standards for electrical units

International measurement standards reproduce the exact values of physical quantities and are used as a reference for calibrating other measuring instruments (MIs). These standards are maintained by international organizations, in particular the International Bureau of Weights and Measures (BIPM). In the modern International System of Units (SI), quantum measurement standards are of utmost importance for the implementation of its units and ensuring metrological traceability to them. Their main feature is that they are based on fundamental quantum effects, which are extremely stable, universal and reproducible anywhere in the world. The main purpose of international quantum measurement standards is to establish a reference for global metrological traceability of measurements, which is based on comparisons of these standards with national measurement standards and precision calibrations of the latter. This process is facilitated by the implementation of the International Committee of Weights and Measures (CIPM) Agreement on the Mutual Recognition (MRA) of National Measurement Standards, Calibration Certificates and Measurements Issued by National Metrological Institutes. The international quantum measurement standards of the Volt and Ohm are maintained by the BIPM. They are of paramount importance for the implementation of the SI units of electrical quantities and for ensuring global metrological traceability. The comparison of these standards plays a key role in the implementation of the CIPM MRA. Only a few NMIs maintain national measurement standards based on the quantum Josephson and Hall effects, which partake in special BIPM key comparisons. The smallest measurement uncertainty of 0.2 nV has been achieved during the comparison of Josephson standards. The smallest relative measurement uncertainty from 3.8×10–9 to 4.6×10–9 has been achieved during the comparison of Hall standards.